As is known, coke ovens may be equipped with one or more offtakes to carry away the volatile products liberated in the coking process. The volatile products pass through a duct in the top of the oven and enter a refractory-lined standpipe, usually called an "ascension pipe", which is connected through a supply pipe to a gas-collecting main. The inner periphery of the ascension pipe is lined with refractory bricks or some other type of refractory material. Steam and water are commonly injected into the supply pipe or the ascension pipe itself to clean the issuing gases prior to the time that they enter the gas-collecting main.
The ascending gases in an ascension pipe of this sort often form carbonaceous deposits on the inner wall of the refractory lining. The deposits must be periodically removed either by attempting to burn them from the refractory walls or with the use of scrapers which are lowered on chains into the ascension pipe and repeatedly moved up and down within the pipe to remove deposits from the refractory walls. The use of these mechanical devices, however, may destroy part of the refractory lining; whereas burning of deposits pollutes the environment. As will be understood, deposits of this type on the inner lining of ascension pipes are highly undesirable and impede the operation of the coke oven.